Talk:GRACE and GRACE-FO

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Fallacy of the GRACE Project, Gravity from Space not the same as Gravity on surface of the planet.
I also noted this on the Gravity on Earth (talk) page.

Looking at the GRACE project Geoid, I quickly noticed that the highest gravity is at the mountain ranges (Andes, Rockys, Himalayans, etc.). This would be the gravity as seen from space which would include the highest mountain peaks (more rock), and parts of the planet closest to the satellite.

The problem is that the gravity experienced at the surface of the earth is also dependent on the distance from the center of the Earth. So, the gravity experienced at the surface of the earth from the highest peaks is actually LOWEST. In fact, in the Gravity on Earth page, it says that the gravity at the peak of Mt. Everest decreases by 0.28%, or 9.8 m/s2 --> 9.77 m/s2.

The Grace Geoid also doesn't seem to take into account the Centrifugal effects on gravity as experienced in the equatorial regions, or the effects of the "bulge" which effectively increases the altitude in the equatorial regions.--Keelec (talk) 03:50, 13 December 2010 (UTC) — Preceding unsigned comment added by Keelec (talk • contribs)


 * Except that Wikipedia is not a source of original research, so unless you find secondary sources discussing the same thing, it's pretty much moot. –  Ker αun oςc op ia◁ galaxies  18:44, 9 March 2011 (UTC)


 * It doesn't show gravity, it shows gravity anomaly. But, ditto above, without secondary sources - -original research. — HELL KNOWZ  ▎TALK 22:38, 15 February 2012 (UTC)

GRACE doesn't measure gravity as experienced on the surface of the earth (what you're talking about, Keelec); it's measuring the variations in the earth's gravity field as sensed from orbit, which is determined by the arrangement of the mass constituting the earth. This is not a "fallacy" of GRACE, but simply a different thing being measured. The GRACE results don't mean you will experience the highest gravity when standing on top of the mountain ranges - it means that if you're a satellite orbiting above the earth, you will be pulled by more gravity when you're above the ranges, since there is more mass beneath you. Is there some clarification needed in the text on the page to make this more clear, somehow? Is this a likely misunderstanding that could arise, or is Keelec's interpretation uncommon enough that it should be ignored? 68.91.91.33 (talk) 22:11, 6 March 2012 (UTC)

Mission objectives to compare with GOCE
GOCE has a Mission objectives section which states the expected accuracy of measurements. It would be great if this article on GRACE also had, so we can more easily compare the missions. - Rod57 (talk) 08:56, 20 November 2012 (UTC)

AR5
GRACE is this basis for improved mass-balance estimates for Antarctica and Greenland in the IPCC AR5; we should add that here William M. Connolley (talk) 22:00, 30 September 2013 (UTC)

Love the added link. 👍 Cloudy SkyView (talk) 15:16, 18 November 2016 (UTC)

Ocean bottom pressure
If ocean bottom pressure is "as important to oceanographers as atmospheric pressure is to meteorologists", why don't we have an article on it? 23.233.82.54 (talk) 00:38, 20 November 2016 (UTC)

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Miscellaneous Edits (March 2018)
Hello,

What do you think about the following edits?

"...atmospheric reentry of GRACE-1 is predicted to occur in late February 2018." >> "...atmospheric reentry of GRACE-1 is predicted to occur in March, 2018." [2]

"During normal operations, the satellites were separated by approximately 200 km along their orbit track." >> "During normal operations, the satellites were separated by 220 km along their orbit track. This system was able to gather global coverage every 30 days." [3]

"Scientists use GRACE data to estimate ocean bottom pressure—as important to oceanographers as atmospheric pressure is to meteorologists." >> "Scientists use GRACE data to estimate ocean bottom pressure (the combined weight of the ocean waters and atmosphere), which is as important to oceanographers as atmospheric pressure is to meteorologists [use same citation]. For example, measuring ocean pressure gradients allows scientists to estimate monthly changes in deep ocean currents.[4] The limited resolution of GRACE is acceptable in this research because the ocean currents are so large, and because deep ocean current estimates can be verified by an ocean buoy network. [5] Scientists have also detailed improved methods for using GRACE data to describe Earth's gravity field (Watkins, et al, 2015).[6]"

Thanks! Emcon789 (talk) 19:50, 11 March 2018 (UTC) Emcon789


 * , I've already updated the reentry for GRACE-1, occurred on 10 March 2018. I'll link your draft so people can see the references. The other points look good too. After you make your edits, I'll tidy up and fully format the citations. If you ever have any questions about Wiki, formatting, standards, whatever, just let me know. Same goes for your classmates. You'll find plenty of folks around the spaceflight community that will prove helpful. — Huntster (t @ c) 00:55, 12 March 2018 (UTC)


 * Thank you! Emcon789 (talk) 02:11, 15 March 2018 (UTC)Emcon789


 * These look like solid additions to the information. I'm glad you added some more background info on ocean bottom pressure, that was definitely necessary. Wike4167 (talk) 18:08, 21 March 2018 (UTC)Wike4167

Hello all, I'm proposing adding these edits to the GRACE Follow-On. Let me know what you think or if I should change anything. Bamsberry (talk) 15:41, 20 March 2018 (UTC)

Bolded sections are proposed edits

"...The ranging system is sensitive enough to detect separation changes as small as 10 micrometers (approximately one-tenth the width of a human hair..>>or approximately the diameter of a blood cell NASA) over a distance of 220 kilometers.[4]"

GRACE Follow-On

NASA and the GFZ Potsdam have announced a follow-on of the GRACE mission. The GRACE-FO mission will be a collaboration between NASA and GFZ and is scheduled to be launched on 28 April 2018 aboard a SpaceX Falcon 9 rocket from Vandenberg AFB, California, sharing the launch with Iridium.[33][34][12]

The orbit and the design of GRACE-FO will be very similar to GRACE. In addition to the proven microwave ranging system used on the GRACE mission, the distance between the two spacecraft of GRACE-FO will also be measured with laser ranging as a technological experiment in preparation for future satellites,>>'''marking the first time an active laser ranging interferometer will be used between two spacecraft. NASA'''.[35][36] '''The addition of the laser interferometer will allow scientists to measure the angle between the two spacecraft, allowing for increased precision and improvements in accuracy. NASA'''

'''GRACE-FO will continue monitoring Earth's gravity and climate. The mission will track changes in global sea levels, glaciers, ice sheets, as well as large lake and river water levels, and soil moisture.'''


 * This all looks good. One tiny thing is that I think for grammar's sake you should change the last sentence to "The mission will track changes in global sea levels, glaciers, and ice sheets, as well as large lake and river water levels, and soil moisture." Emcon789 (talk) 02:31, 21 March 2018 (UTC) Emcon789


 * These look like valuable contributions, except for the addition about the size of a tenth of a micron. It would not hurt the article, but I don't think it is necessary because of the current size comparison already being there. I also agree with Emcon's comment about grammar additions. Wike4167 (talk) 18:08, 21 March 2018 (UTC)Wike4167

Hello everyone, I am proposing an edit under the "Other Signals" section.

Starting a new paragraph at the bottom of the this section, I would add: "Data from GRACE has improved the current Earth gravitational field model, leading to improvements in the field of geodesy. This improved model has allowed for corrections in the equipotential surface which land elevations are referenced from. This more accurate reference surface allows for more accurate coordinates and for less error in the calculation of geodetic satellite orbits."  Wike4167 (talk) 23:34, 20 March 2018 (UTC)William Keenan


 * Good elaboration. Some small suggestions: "Data from GRACE has improved the current Earth gravitational field model, leading to improvements in the field of geodesy. This improved model has allowed for corrections in the equipotential surface from which land elevations are referenced. This more accurate reference surface allows for more accurate coordinates [maybe be more specific than 'more accurate coordinates'?] and for less error in the calculation of geodetic satellite orbits." Emcon789 (talk) 02:31, 21 March 2018 (UTC) Emcon789


 * My suggestions would be the same as Emcon789's otherwise I think you did a nice job. I'm not sure if I would add this to the section of "Other Signals," though. It kind of matches that content but may or may not need a new section of its own. Bamsberry (talk) 07:06, 21 March 2018 (UTC) Bamsberry

differential wavefront sensing
"Wavefront sensing" is linked to an existing stub article which lists 9 different types. It would be useful for this article to describe the particular type installed on the satellites.71.230.16.111 (talk) 02:06, 7 May 2020 (UTC)
 * I've added a citation which has all the relevant information. It isn't clear from the description there that any of the "wavefront sensing" links describe the system used by GRACE-FO, so I removed the wavefront sensing wikilink. But I don't care that much if someone wants to put it back. Dan Bloch (talk) 03:53, 7 May 2020 (UTC)